This invention relates to a process for treating waste water containing cellulose nitrate particles and, more particularly, to a process for the chemical-biological degradation of cellulose nitrates found in waste streams resulting from cellulose nitrate manufacture so as to produce an effluent substantially free of reduced and oxidized forms of nitrogen.
Cellulose nitrate, hereinafter referred to as "nitrocellulose", is produced in large quantities for use in the manufacture of munitions, synthetic finishes and a wide variety of other products, by the reaction of pure cellulose with an excess of nitric acid and a dehydrating agent such as sulfuric acid. In the manufacture of nitrocellulose, the freshly nitrated cellulose material is thoroughly washed with substantial amounts of water to remove excess acid present and this wash water carries, in addition to unreacted acid, a suspension of small particles of insoluble nitrocellulose referred to as "nitrocellulose fines." While the waste water is normally neutralized and treated before flowing into the receiving water, there has, heretofore, been no practical way to eliminate the nitrocellulose fines therefrom, which fines constitute a serious waterway pollutant. Nitrocellulose fines remain in suspension in moving waste streams and receiving waters and this particulate suspension creates a milky appearance in the water, a discoloration that is objectionable from an aesthetic standpoint and one which prevents the use of such waters for domestic consumption or for many industrial uses. Another problem arising from the discharge of nitrocellulose into receiving waters is the likelihood of concentration of these nitrocellulose fines in pools located along stream and river beds which concentrated deposits could suddenly explode should they become dessicated or come into contact with strong oxidizing agents. If filtration were to be employed downstream of such a waste discharge for any purpose, the fines would collect on the filter device to an extent sufficient to constitute a serious hazard.
Attempts to quantitatively separate the nitrocellulose fines from the waste stream output of a producing plant by mechanical means, i.e. sedimentation, filtration and centrifugation have not proved to be fully adequate and even had such efforts beeen totally successful, would pose a further problem with respect to handling and disposing of the concentrated fines in an environmentally acceptable and safe manner. Nitrocellulose, being a thoroughly substituted cellulose compound is not subject to direct microbiological attack and is not broken down by microbes in receiving water systems. Therefore, there exists a need for a method for removing and disposing of these insoluble and non-biodegradable nitrated cellulose products from the waste streams of nitrocellulose producing plants without further reducing the quality of the environment. This invention has as one of its objects the provision of a practical and effective chemical-biological method for disposal of nitrocellulose fines without creating other toxic products. Another object of this invention is to provide a method for the treatment and purification of other polluting waste streams normally found associated with industrial facilities, i.e., raw domestic sewage and water-dry waste streams (typically aqueous waste streams bearing organic liquids or solvents).